Patients with AIDS resulting from HIV have essentially no cell-mediated immunity. Therefore, their innate immune responses become critical for protection from secondary infections. Members of the herpesvirus family including HSV, CMV, EBV, KSHV, and VZV are major contributors to secondary infections in the oral cavity of AIDS patients. Interferons are the primary antiviral cytokine produced by virus infected cells. IFNs play a major role in the innate antiviral immune response, repressing viral gene expression very early in infection, presumably at the nuclear sites of viral genome deposition, adjacent to the ND10 nuclear body. IFNs induce expression of two families of nuclear proteins, namely PML and Sp100, which associate with the ND10s and appear to participate in repression of viral gene transcription. To study the mechanisms of this inhibition, members of the PML and SP100 families of IFN-inducible nuclear body proteins will be characterized in transcription repression assays for inhibition of basal and viral transactivator-induced gene expression. In addition, two newly described proteins, namely MZF1B and RAZ1, which form nuclear complexes termed REMs, which repress activity will be examined. Using both transient and stably transfected cells, the specificity of the repressors, used alone or in combination will be examined using chemiluminescence assays for reporter gene expression. Nuclear localization of the repressors and co-localization with ND10 structures will be examined in cells treated with IFN, in cells infected with HSV, and in the absence of treatment or infection. To understand the mechanisms of action of repressors, proteins with which they associate will be identified by co-immunoprecipitation assays and yeast two-hybrid analysis. The association of REM proteins with a major transcriptional activator of HSV will be characterized. The IFN-responsiveness of REM proteins will be measured. The localization of viral DNA with the novel nuclear structures will be determined. Understanding specificity of the repression of viral gene transcription by IFN-induced and other nuclear proteins and the mechanisms by which repression occurs should provide insight into how the cell combats viral infection. This understanding should allow the development of strategies for treatment of secondary viral infections in the oral cavity of HIV-infected individuals that enhance or mimic these repressive activities.